Whenever reported, instances of SCP-XXXX-1 are to be apprehended and sent to the care of the Curtis Steiner Facility for Print-Based Anomalies in Baltimore, MD.

I have issues with named facilities like this, but I'm new, so chalk that up to personal preference. One thing I do have an issue with is what do you mean by reported? It required a little elucidation: are the Foundation actively looking for them? What are the protocols for civilians finding such a thing? Are they mailed to the facility or are additional precautions necessary?

incinerated after they have been studied.

Again, personal preference, but I'd like more detail about what constitutes "studied". Even something akin to "thorough forensic analysis prior to incineration" feels preferable. Just calling it study feels boring.

Center personnel will determine

I believe proper protocol is to call personnel by the Center's title, meaning Wettsworth. This should go as "Wettsworth personnel will determine…" Center by itself is a little vague.

Center personnel will determine … for each individual within the facility

This here certainly needs little more work. They determine the accommodations for themselves? I'm not quite sure what this is supposed to imply. Are managers of some sort studying accommodations routinely? Are all workers doing that? This is a really confusing sentence.

All such individuals, however, are to be kept under observation at all times.

By who? Is this referring to those, whomever they may be, that allocate accommodations in the previous entry? Is it by outside staff? Are they under CCTV surveillance or something else?

Secondly, is this only in reference to written communication, or degrading mental condition. Something else?

They are to be prevented from engaging in any form of written communication at all costs.

While it is good to leave some things ambiguous in order to give the recipient of this dossier a little leeway in dealing with emergencies, a little more description does help at times. What does "at all costs" mean? A double tap to the chest? Confinement?

They are not to leave Research Center Grounds.

Here's where I get a little lost. Is this a Foundation facility? Are those in the facility Foundation employees? Why are the Foundation willingly sending these items to this facility and appearing to do nothing to minimize exposure to the effects?

If these are not Foundation employees, why are they not allowed to leave the grounds when it is apparently a normal facility? If it is, it is very ambiguous who is supposed to be suffering these effects and who is not.

between 1 and 5 deceased

It varies between writers, but the more common method to express numbers is this: "between one (1) and five (5) decreased". It's for the same reason why many writing guides spell "okay" and not "OK". The second is more bold and jarring, wile the former looks more naturally like a word. Mixing letters and numbers, while not completely jarring out of immersion, is still a little awkward to read.

organs and instead filled

and are instead filled

and ultimately, brain death.

"and, ultimately, brain death." Missing comma there.

consistent pattern beyond this has been discovered

I'd pick a different word or phrase rather than pattern. It's not really a pattern, more of a method or tactic really.

is currently deemed unfeasible.

I'm suspicious about that word "unfeasible". That implies there may be a way but that it is not worth it. Are there means to reverse it? Or does it mean that the only thing the Foundation can do is slow it?

will invariably result in the creation of another instance of SCP-XXXX-1

I find this odd as this SCP literally rots the brain. Would there be a stage where they become harmless because of the degradation? Earlier it gives the impression that it slowly kills people by turning the brain into Flubber. That pretty much results in death because the body needs the brain to live. Now the dossier is telling me that instead it rots the brain, AND creates a self perpetuating compulsion. I'm getting the impression your idea changed halfway through the article.

subjects brain matter has been replaced with SCP-XXXX-2

As in the exoskeleton itself? The brain matter in it? Both? For that matter, when a letter is mailed, does the bug contain the guy's own brain matter or someone else's? This raises a couple questions about further testing required for this SCP.

visible signs of tampering.

On a more comedic note, the last time I heard context like this was akin to "Using my high intelligence stat, I skillfully take apart his skull with a crowbar."

But seriously, how do you tamper with a living human skull? I think another word or phrase is needed there.

tampering.
The first instance

Is there a hidden newline character in there?

in ██ countries internationally

When speaking of countries, adding internationally in this context is unneeded. It can be removed.

past 5 years

Again, spell it out fully.

In our history as a group, our mission has been simple: to give you what you want. And now,
with Our Investment, we believe we've finally found the potential to make everyone see that we
have only their best interests in mind.

As it's a transcription, I'm not complaining if this is how it is supposed to be, but if it is not, you have newline characters in there.

One last thing I believe you should think about after the rewrite is whether or not it deserves a keter designation. In my mind it makes a firm Euclid because I don't see the Foundation expending much resources or scrambling to contain the effects of this particular skip. On the other hand, there were numerous things about this skip that were too vague, so the designation depends on your rewrite. I don't feel like it earns it.

Personally I would class this as Euclid. I think that, during a containment breach, they'd easily be able to contain these. This doesn't really pose a massive threat to anyone and there are steps that can be taken to help negate receiving the effects of the skip (such as reading a transcript)